POSTTRANSCRIPTIONAL BLOCK IN OXYTOCIN GENE-EXPRESSION WITHIN THE SEMINIFEROUS TUBULES OF THE BOVINE TESTIS

Northern blot hybridization showed that bovine and sheep testis, unlik e testes from other mammals, contain moderate levels of an apparently normal oxytocin gene transcript. In Situ hybridization localized this mRNA to within the seminiferous tubules, possibly in the Sertoli cells . Conflicting with this result, immunohistochemistry showed that both oxytocin and the syngeneic neurophysin I epitopes are both clearly res tricted to the Leydig cells, being expressed here at a low level. Sinc e illegitimate transcription from spurious start sites can lead to a l ack of translation product, the integrity of the major ruminant testic ular transcripts of the oxytocin gene was checked using differential h ybridization, RNase protection and multiple polymerase chain reaction assays. All tests showed the transcripts to have a normal, translatabl e composition and to be transcribed from the conventional 5' initiatio n site. Therefore, the block in oxytocin gene expression within the tu bules is probably due to a lesion at the post-transcriptional level. T he low level peptide expression in the Leydig cells can probably be at tributed to the presence of functional transcripts in these cells, whi ch are below the level of significant detection for the in situ hybrid ization assay.